In electrical networks such as vehicle electrical systems that receive electrical power from a battery, it is important, in particular from the standpoint of safety aspects, to know the prevailing battery performance. In the area of automotive engineering, it is known that the state of charge (SOC) or the state of health (SOH) of the battery may be calculated from the prevailing operating parameters of the battery, in particular the battery voltage, the battery current and the battery temperature. This type of battery state detection provides information about the state of charge and/or the state of health of the battery, but it does not provide any information about the power actually deliverable or the withdrawable charge of the battery. For this reason, mathematical models of energy accumulators have already been proposed so that the chargeability, i.e., the withdrawable charge of an electrical energy accumulator, may be determined with greater precision. These are mathematical models that represent the electrical properties of the energy accumulator on the basis of various mathematical equations. These mathematical equations describe functional relationships among various state variables, e.g., battery internal voltages, currents, etc., and include various parameters that map the electrical and, if applicable, also thermal properties of the energy accumulator.
Known battery models usually include a state variable and parameter estimator, stored as software in a control unit with which the various state variables and parameters of the energy accumulator model are calculated, and a predictor capable of making a prediction about a future battery state (e.g., a battery voltage) or about the charge withdrawable from the battery, taking into account a predetermined charge profile, e.g., a current characteristic or a charge characteristic. However, known state variable and parameter estimators yield relatively inaccurate results for the desired parameters, in particular for the capacitance or the internal resistance of the battery, and therefore are not suitable for a model-based prediction or have a relatively complex structure.